Study on the 4-channel micro-monolithic design with geometry control for reversible solid oxide cell

Reversible solid oxide cell (R-SOC) has been attracting considerable attention as a technology capable of power generation and CO2 electrolysis. In addition to new material development, innovation in structural design is also a decisive factor. In this study, a 4-channel micro-monolithic design, in the form of a tear-drop inner channel structure, was successfully developed. The micro-monolith obtained includes plurality of micro-channels growing from multiple directions and spongy active regions near the exterior surface. Uniquely, the irregular tear-drop inner channels further increase the proportion of the electrochemically active region to the overall circumference, achieving more efficient utilization of the geometric surface area. Such micro-structured cells with Ni-YSZ/YSZ/YSZ-LSM materials exhibited effective performance in the reversible operation of R-SOC. A superior performance of 1.20 W·cm−2 at 800 ℃ for H2 fuel cell was demonstrated. Similarly, during the electrolysis of CO2, current density recorded by the cells reached 1.20 A·cm−2 at 1.5 V and 800 ℃, which is competitive compared with the values of the previous design investigations. Relatively low diffusion polarization shown in electrochemical impedance spectroscopy (EIS) suggests that this is due to the very gas transfer resistance in the fuel electrode. This novel multi-channel micro-monolithic structure shows a potential to substitute the conventional tubular counterpart.